This invention relates to an elastomer of copolymer made up of a vinyl carboxylate, ethylene, an alkyl acrylate and/or an alkoxyalkyl acrylate, and a monoalkoxyalkyl maleate. This invention also relates to vulcanized products of said elastomer.
Heretofore, there have been provided elastomer compositions containing a copolymer made up of a vinyl carboxylate, ethylene, an alkyl acrylate and/or an alkoxyalkyl acrylate, and a monoepoxy monoolefinic compound (e.g. glycidyl methacrylate) as a cure site monomer (cf. U.S. Pat. No. 4,303,560 corresponding to Japanese Patent Kokai Koho Nos. 55-123641 and 55-123611.)
These elastomer compositions can be vulcanized by using a vulcanizing agent such as an aliphatic acid soap/sulfur, polyamines, a carboxylic acid or ammonium salts thereof, and the vulcanized products are improved in the heat resistance, oil resistance and weatherproof as well as mechanical properties. The compositions, however, have unnegligible problems in their curing rate.
That is to say, they often require post cure after the usual vulcanization whereby covering their low curing rate and obtaining a product of desired properties. The post cure, in fact, enables the vulcanized product to have an improved compression set. If the post cure step, however, can be performed in a shorter time or utterly omitted, the vulcanized products may be manufactured more advantageously in a commercial scale. Therefore, elastomers having good vulcanizate properties have long been expected.
Heretofore, there have been reported many studies on new copolymer elastomers and vulcanizing agents therefor to attain more rapid and more effective vulcanizing procedure. For example, U.S. Pat. No. 3,883,472 discloses the fact that faster cures may be attained by using compositions containing elastomeric copolymer made up of an acrylate, ethylene, and a monoester of butenedionic acid. These elastomers of acrylic ester type copolymer using the monoester of butenedionic acid (e.g. monoalkyl maleates) as a cure site monomer have, in fact, faster curing rate. However, they have disadvantageous tendency of scorching (a phenomenon of an early-time vulcanization).